Refining of petroleum crude minerals to excise therefrom a variety of lubricating oils which can function with a high viscosity index has become an extremely complex and developed area of invention and experimentation. In treating heavier oils, such as bright stock raffinates, a ZSM-5 catalyst has no peers. However, in treating light lubricating oils such as a HVI 100 or 150, it has been found that a higher viscosity index is retained if the oil is dewaxed in the presence of a ferrierite catalyst having metals incorporated therewith. The synthetic ferrierite may be prepared by such processes as described in U.S. Pat. Nos. 3,966,883; 4,000,248; 4,017,590; and 3,933,974, all of the disclosures of which are herein incorporated by reference.
One process which teaches catalytic hydrodewaxing of a petroleum feedstock, such as distillates and residual fractions, occurs in the presence of a catalyst comprising a synthetic ferrierite zeolite with at least one metal from the group consisting of Group VIB, Group VIIB and Group VIII metals incorporated therewith. In 1982, U.S. Pat. No. 4,343,692 issued to Winquist for such a process having unrecognized advantageous viscosity index retention. The instant invention is concerned with a time efficient method of manufacture of a catalyst composition of matter precursor whose dewaxing abilities (after conversion to the hydrogen species) were adroitly promulgated by Winquist, in U.S. Pat. No. 4,343,692.
One method of preparing a catalyst used in the last mentioned patent is a process for preparing ferrierite as described in Nanne et al U.S. Pat. No. 4,251,499. The molar compositions of the starting material in Nanne et al are exemplified by 13 different examples, nine of which resulted in the production of relatively pure ferrierite. The starting components of alumina and sodium oxide to silica vary to an extent both smaller and larger than the narrow range of this invention. Regardless of the mole ratios taught in Nanne et al, a reaction time of at least 113 hours is described for the preparation of a catalyst with sufficient catalytic activity to result in high VI lubricating oils via dewaxing of a wax-containing lubricating oil. This invention is an improvement upon the method of manufacture of the ferrierite catalyst of Nanne et al and a step forward in the art of catalyst preparation techniques.
In the Journal of Catalysis, Vol. 35 at pages 256-272 (1974), an article by C. L. Kibby et al describes the composition and catalytic properties of synthetic ferrierite. The time of preparation was greatly shortened by the seeding with crystals of 10 to 100 microns at 310.degree. C. Recognition is made in this publication that once activity begins to inure to the synthetic ferrierite, it comes very quickly and ultimate catalytic activity is rapidly accomplished. Also, cognizance is made of the fact that heating of the aqueous mixture beyond the time required for essentially complete crystallization does not seem to have either a deleterious or an enhancing consequence upon resultant catalytic activity. As shown in the data of this case, this has now been discovered to be not a completely accurate statement at least as it applies to extended crystallization of sodium ferrierite within the molar ratio recipes of this invention.
In Cormier et al, U.S. Pat. No. 4,017,590, a synthetic ferrierite is prepared within 2-96 hours at 230.degree.-310.degree. C. without the use of a nitrogen template precursor. The mole ratios of aluminum and total alkali are much larger than contemplated in the instant invention plus a carbonate-bicarbonate buffer is maintained during crystallization. The sodium ferrierite catalyst precursor of this invention is prepared, i.e. crystallized, without the presence of carbon dioxide. Also, employment of large quantities of aluminum in Cormier et al would not result in incomplete crystallization of sodium ferrierite.